Community weight loss programmes, such as Weight Watchers, are effective at helping people to lose weight, our latest research shows. We found that a three-month programme helps people lose weight, but a one-year programme helps people lose more weight for longer and reduces their risk of developing type 2 diabetes. Wider availability of these programmes could help people avoid metabolic diseases, such as diabetes, and may even save the NHS money in the long run.

Obesity increases people’s risk of developing illnesses such as type 2 diabetes, heart disease and some cancers. In the UK, where almost two-thirds of adults are overweight or obese, some GPs are tackling this problem by referring their patients to community weight loss programmes.

The UK’s National Institute for Health and Care Excellence (NICE), the agency that decides which medicines and treatments are appropriate for the NHS to fund, recommends that adults who are obese are referred to a structured weight loss programme for at least three months. The NICE guidance specifically highlights community weight loss programmes as both cost-effective and evidence-based interventions. However, research published in BMJ Open in 2015 revealed that over a seven-year period only 6% of obese adults received a referral to any form of weight management service, let alone an evidence-based programme.

Low referral rates can be partially explained by the reluctance of GPs to raise the issue of weight with their patients and a lack of confidence in the effectiveness of these programmes. But even when GPs are willing, there are limited services available to refer patients to. Coverage of weight management services across the UK is patchy and the quality of the services is variable.

The longer the programme, the better

In our study, published in The Lancet, we compared the effectiveness and cost-effectiveness of three treatment options: referral to Weight Watchers for three months, referral to Weight Watchers for one year, and a brief intervention (one-off advice together with a self-help booklet).

We recruited 1,267 overweight or obese adults from 23 GP clinics across the UK and randomly allocated them to one of the three interventions. Over a two-year follow-up, those who were referred to Weight Watchers lost more weight than those who were in the self-help group. And those in the one-year programme lost more weight than those in the three-month programme.

A year after the intervention ended, those in the one-year programme had lost on average 6.8kg, compared with 4.8kg in the three-month group, and 3.3kg in the advice and self-help group. At two years, all groups had regained some of the weight, but those given a year-long programme were still lighter than the other groups. Those in the year-long programme had lost 4.5kg since the trial started, compared with 3kg in the three-month programme and 2.3kg in the brief intervention group.

Compared with participants in the other groups, those in the year-long programme also had significantly greater reductions in fasting blood glucose and glycosylated haemoglobin, which are important markers of the risk of developing diabetes.

Modelling the long-term impact

To understand the long-term cost-effectiveness of these programmes, we modelled their impact over 25 years. Modelling uses assumptions as well as hard data, which might cause scepticism, so in our modelling we tried to make conservative assumptions – such as assuming that all weight lost was regained after five years and that the full cost of the programme was incurred if people attended one session (when in practice this might not be the case).

With this model we found that, compared with the self-help group, the three-month programme achieved greater reductions in weight-related illnesses. Cost-savings on NHS treatment outweighed the cost of the programme – a net saving of about £2.68 per person referred.

The year-long programme achieved greater weight loss for longer, so led to even bigger reductions in illnesses. The extra costs of the year-long programme were not offset by savings on NHS treatment costs (the additional treatment cost was estimated at £49 per person), but it was still very cost-effective by NICE standards. The benefits may even be underestimated because our model did not include potential savings in social care and indirect healthcare costs.

While modelled data does not provide the same level of evidence as the findings from the randomised controlled trial, it does add to previous evidence that these programmes are a cost-effective treatment option.

So what barriers might prevent greater investment in them? Community weight loss programmes are commissioned by local authorities, but our data shows the benefit as being a reduction in NHS treatment costs (that is, a different department), and only in the long term. The focus on savings in NHS treatment costs may distract from the wider social and economic benefits of a reduction in obesity, which are not captured in current cost-effectiveness models.

With constrained budgets and short parliaments, local authorities may struggle to take the necessary long-term perspective and may focus on what they can afford now. While this is understandable, it may mean we miss a vital opportunity to provide effective treatment options to millions of people who need them.